SUMMARY

The aerodynamic characteristics of an airfoil are modified using active fluidic-based flow control over a range of angles of attack with specific emphasis on control in the absence and presence of stall. The first part of this dissertation focuses on mitigation of static and dynamic stalls at moderate to high angles of attack using pulsed actuation near the leading edge by combustion-powered actuators. It is shown that the actuation on static and pitching/plunging model effects rapid, accelerated flow reattachment and consequently increased lift performance and improved damping stability. The second part of the dissertation extends the application of active flow control to moderate and low angles of attack when the base flow is fully attached for time-dependent, bi-directional regulation of the aerodynamic loads using independently controlled high aspect-ratio spanwise trailing edge actuation jets on the pressure and suction sides. The transitory characteristics of the flow are investigated using time-resolved measurements of the aerodynamic loads with highlights on the temporal response following the onset and termination of the actuation along with corresponding measurements of the unsteady velocity field near the trailing edge using phase-locked particle image velocimetry. It is shown that coupled pulsed actuation on the pressure and suction surfaces leads to rapid bi-directional changes in lift with characteristic response time in the same order of magnitude as the airfoil convective time scales, along with reduction in drag. Phase-locked velocity measurements near the trailing edge demonstrate bi-directional cross stream transport of vorticity concentrations, modification of the trailing edge Kutta condition, and the temporal manipulation of vorticity flux into the near wake.